Coins are commonly used as a means of payment in vending or similar automatic machines. In this function, the coin needs to be recognized and identified by the machine and either accepted or rejected. This discrimination process is carried out by a device called a coin acceptor and generally consists of measuring various physical properties of the coin as it move's through the acceptor's mechanism.
Most coin acceptors presently in use rely on signals that result when a coin disturbs a variable electromagnetic field. For example, a coin moves between two coils acting as emitting and receiving antennae, respectively. The signal picked up by the receiving coil is then analyzed using a proprietary algorithm to produce what is called an electromagnetic signature (EMS) of the coin. Based on its EMS, the coin is either accepted or rejected.
A common problem affecting coin acceptors is the fact that electromagnetic signatures (EMSs) may be very similar for different coins. When the EMSs of coins of different denominations or coins issued in different jurisdictions are similar, there is an opportunity for fraud.
As referenced above, EMS values are not calculated by any physical, chemical or mathematical formula. Rather, they are a set of numbers generated by software and algorithms devised by each coin acceptor mechanism manufacturer. EMSs are unit-less and are made up of a set of figures which are purported to determine the diameter, the edge thickness, the weight, the alloy composition, etc., of a coin at different frequencies. Moreover, these values are not single repetitive values which identify the characteristics of the coin. Rather than being exact; the values vary from coin to coin within a certain range. Accordingly, that range is critical for coin acceptor manufacturers, since even perfectly valid coins may be rejected. The range of values must therefore be established so as to properly characterize the specific properties that identify the particular features of a coin, such as its diameter, edge thickness or alloy.
Perhaps one of the best ways to relate an EMS to a known physical measurement is through the metal's conductivity. Commercial instruments are available to measure conductivity, such as the Dr. Foerster's™ Sigma D conductivity meter and the Fischer Sigmascope® SMP10 conductivity meter.
With base metals increasing in price over the last 30 years, people working in the minting industry have come up with ideas on how to reduce the cost of producing coins, including finding metal substitutes for more expensive base metals, such as nickel and copper. Substitutes include mono-ply plated steel products. Mono-ply plated steel consists of plating a single layer of a metal or an alloy over steel. This is to be distinguished from multi-ply plated steel, which consists of plating several layers on steel.
Sample patent applications and patents that describe mono-ply plated steel include the following: Canadian Patent Application No. 2,137,096, Canadian Patent No. 2,271,654, U.S. Pat. No. 4,089,753, U.S. Pat. No. 4,247,374 and U.S. Pat. No. 4,279,968. Alternatives include coins in which the core is made of a metal, such as nickel or copper, which is mono-ply plated with either another metal or an alloy. Sample patents of this type include U.S. Pat. No. 3,753,669, U.S. Pat. No. 4,330,599 and U.S. Pat. No. 4,599,270.
Inconveniently, coin acceptor mechanisms in the vending industry often cannot differentiate between coins from different countries that are made of the same alloy and have approximately the same diameter, thickness and weight. In addition, mono-ply plated steel coins have EMSs that are so variable and so close to that of steel that many vending machines cannot be calibrated to differentiate between regular steel and mono-ply plated steel.
Metal disks, especially coins, have been produced so as to be distinguishable and separable from one another on the basis of their magnetic properties. As proposed by German Patent Application DE 3207822 and U.S. Pat. No. 3,634,890, laminate metallic claddings suitable for coin production include magnetizable metals (such as nickel) as well as non-magnetizable metals (such as a copper-nickel alloy containing 5 to 60 percent nickel). Along the same lines, U.S. Pat. No. 4,973,524 describes a method of making coins that are a suitable as an alternative to nickel-containing coins, the method comprising the steps of forming a laminated composite comprising a core layer of a first corrosion-resistant steel, such as ferritic-chromium steel, and cladding layers on opposite sides of this core layer with a second corrosion-resistant steel, such as austenitic nickel-chromium steel.
Despite the above, counterfeiters are actively finding ways to get past the electronic devices used in vending machines, and therefore fraud continues to be a major problem. There thus remains a need for novel coins that combine metals that are favored by manufacturers of legal tender but that may be discriminated on the basis of their EMSs.
The present invention seeks to meet this and related needs.